The suitability of sentinel species to monitor environmental pollution is often hampered by an insufficient knowledge on pollutant trophodynamics. We simultaneously evaluated the influence of individuals’
trophic position (as revealed by d15N values) and dietary exploitation of particular systems (using d13C and d34S as proxies) on inorganic pollutant concentrations measured on fledglings’ feathers of a wide-range
feeder, the Yellow-legged Gull (Larus michahellis), sampled at four locations throughout the Western Mediterranean. Concentrations of total Hg and Se in fledgling feathers (2.43 1.30 and 1.16 0.43 mg/g, respectively) were under the threshold points for deleterious effects on seabirds. On the contrary, alarming Pb concentrations were found in one colony (mean: 1.57 2.46 mg/g, range: 0.16e12.13). With the
exception of Pb, pollutant concentrations were positively influenced by consumption of marine resources (as suggested by the positive relationship with d34S values), whereas trophic position played a minor role in determining pollutant body burdens.